WO2021225338A1 - Image decoding method and apparatus therefor - Google Patents

Abstract

An image decoding method performed by a decoding apparatus, according to the present document, comprises the steps of: deriving a multilayer output layer set (OLS) index of a target OLS in a list of multilayer OLSs; acquiring hypothetical reference decoder (HRD)-related information and decoded picture buffer (DPB)-related information for the target OLS, on the basis of the multilayer OLS index; and decoding a picture within the target OLS, on the basis of the HRD-related information and the DPB-related information, wherein the multilayer OLSs are OLSs including a plurality of layers, and the target OLS is one of the multilayer OLSs.

Description

Video decoding method and apparatus

This document relates to an image coding technology, and more specifically, an image coding image information including HRD-related syntax elements and/or DPB-related syntax elements using a multi-layer OLS index for multi-layer OLS in an image coding system. It relates to a decoding method and an apparatus therefor.

Recently, demand for high-resolution and high-quality images, such as high definition (HD) images and ultra high definition (UHD) images, is increasing in various fields. Since the amount of information or bits to be transmitted increases relative to the existing image data as the high-resolution and high-quality image data increases, the image data can be transmitted using a medium such as a conventional wired or wireless broadband line, or the image data can be saved using an existing storage medium. In the case of storage, the transmission cost and the storage cost are increased.

Accordingly, high-efficiency image compression technology is required to effectively transmit, store, and reproduce high-resolution and high-quality image information.

An object of the present document is to provide a method and an apparatus for increasing image coding efficiency.

Another technical object of the present document is to provide a method and apparatus for signaling HRD-related syntax elements and/or DPB-related syntax elements for multi-layer OLS.

According to an embodiment of the present document, there is provided an image decoding method performed by a decoding apparatus. The method includes deriving a multi-layer OLS index of a target OLS in a list of multi-layer output layer sets (OLS), based on the multi-layer OLS index, HRD (Hypothetical Reference Decoder) related information and DPB for the target OLS Obtaining (Decoded Picture Buffer) related information and decoding a picture in the target OLS based on the HRD related information and the DPB related information, wherein the multilayer OLSs are OLSs including a plurality of layers , the target OLS is one of the multi-layer OLSs.

According to another embodiment of the present document, a decoding apparatus for performing image decoding is provided. The decoding apparatus derives a multi-layer OLS index of a target OLS in a list of multi-layer output layer sets (OLS), and based on the multi-layer OLS index, HRD (Hypothetical Reference Decoder) related information and DPB for the target OLS (Decoded Picture Buffer) an entropy decoding unit for obtaining related information and a DPB for decoding a picture in the target OLS based on the HRD related information and the DPB related information, wherein the multi-layer OLS includes a plurality of layers OLSs, and the target OLS is one of the multi-layer OLSs.

According to another embodiment of the present document, a video encoding method performed by an encoding apparatus is provided. The method includes deriving a multi-layer OLS index of a target OLS in a list of multi-layer output layer sets (OLS), based on the multi-layer OLS index, HRD (Hypothetical Reference Decoder) related information and DPB for the target OLS (Decoded Picture Buffer) generating related information and encoding image information including the HRD related information and the DPB related information, wherein the multilayer OLSs are OLSs including a plurality of layers, and the target The OLS is characterized in that it is one of the multi-layer OLSs.

According to another embodiment of the present document, a video encoding apparatus is provided. The encoding apparatus derives a multilayer OLS index of a target OLS in a list of multilayer output layer sets (OLS), and based on the multilayer OLS index, HRD (Hypothetical Reference Decoder) related information and DPB for the target OLS (Decoded Picture Buffer) generating related information and comprising an entropy encoding unit for encoding image information including the HRD related information and the DPB related information, wherein the multilayer OLSs are OLSs including a plurality of layers, and the target The OLS is characterized in that it is one of the multi-layer OLSs.

According to another embodiment of the present document, there is provided a computer-readable digital storage medium in which a bitstream including image information causing an image decoding method to be performed is stored. In the computer-readable digital storage medium, the image decoding method comprises the steps of deriving a multi-layer OLS index of a target OLS in a list of multi-layer OLS (Output Layer Sets), based on the multi-layer OLS index, the target OLS Obtaining HRD (Hypothetical Reference Decoder) related information and DPB (Decoded Picture Buffer) related information for Multilayer OLSs are OLSs including a plurality of layers, and the target OLS is one of the multilayer OLSs.

According to this document, it is possible to efficiently perform signaling of HRD-related information and DPB-related information by deriving an index of a list for multi-layer OLS among all OLSs, thereby improving overall coding efficiency.

According to this document, it is possible to prevent HRD-related information and DPB-related information signaled only for multi-layer OLS from being mapped to wrong OLS by deriving an index of a list for multi-layer OLS among all OLSs, and through this, overall coding efficiency can improve

1 schematically shows an example of a video/image coding system to which embodiments of this document can be applied.

2 is a diagram schematically illustrating a configuration of a video/image encoding apparatus to which embodiments of the present document may be applied.

3 is a diagram schematically illustrating a configuration of a video/image decoding apparatus to which embodiments of the present document may be applied.

4 schematically illustrates an image encoding method by an encoding apparatus according to the present document.

5 schematically shows an encoding apparatus for performing an image encoding method according to this document.

6 schematically shows an image decoding method by a decoding apparatus according to the present document.

7 schematically shows a decoding apparatus for performing an image decoding method according to this document.

8 is an exemplary view of a content streaming system structure to which embodiments of this document are applied.

Since this document may have various changes and may have various embodiments, specific embodiments will be illustrated in the drawings and described in detail. However, this is not intended to limit the embodiments of this document to specific embodiments. Terms commonly used herein are used only to describe specific embodiments, and are not intended to limit the technical spirit of the present document. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present specification, terms such as “comprise” or “have” are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, and includes one or more other features or It is to be understood that the existence or addition of numbers, steps, operations, components, parts or combinations thereof is not precluded in advance.

Meanwhile, each configuration in the drawings described in this document is shown independently for convenience of description regarding different characteristic functions, and does not mean that each configuration is implemented as separate hardware or separate software. For example, two or more components among each component may be combined to form one component, or one component may be divided into a plurality of components. Embodiments in which each component is integrated and/or separated are also included in the scope of the present document without departing from the essence of this document.

Hereinafter, with reference to the accompanying drawings, a preferred embodiment of the present document will be described in more detail. Hereinafter, the same reference numerals are used for the same components in the drawings, and repeated descriptions of the same components may be omitted.

1 schematically shows an example of a video/image coding system to which embodiments of this document can be applied.

Referring to FIG. 1 , a video/image coding system may include a first apparatus (source device) and a second apparatus (receive device). The source device may transmit encoded video/image information or data in the form of a file or streaming to the receiving device through a digital storage medium or a network.

The source device may include a video source, an encoding apparatus, and a transmission unit. The receiving device may include a receiving unit, a decoding apparatus, and a renderer. The encoding apparatus may be referred to as a video/image encoding apparatus, and the decoding apparatus may be referred to as a video/image decoding apparatus. The transmitter may be included in the encoding device. The receiver may be included in the decoding device. The renderer may include a display unit, and the display unit may be configured as a separate device or external component.

A video source may acquire a video/image through a process of capturing, synthesizing, or generating a video/image. A video source may include a video/image capture device and/or a video/image generating device. A video/image capture device may include, for example, one or more cameras, a video/image archive containing previously captured video/images, and the like. A video/image generating device may include, for example, a computer, tablet, and smart phone, and may (electronically) generate a video/image. For example, a virtual video/image may be generated through a computer, etc. In this case, the video/image capturing process may be substituted for the process of generating related data.

The encoding device may encode the input video/image. The encoding apparatus may perform a series of procedures such as prediction, transformation, and quantization for compression and coding efficiency. The encoded data (encoded video/image information) may be output in the form of a bitstream.

The transmitting unit may transmit the encoded video/image information or data output in the form of a bitstream to the receiving unit of the receiving device in the form of a file or streaming through a digital storage medium or a network. The digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, and SSD. The transmission unit may include an element for generating a media file through a predetermined file format, and may include an element for transmission through a broadcast/communication network. The receiver may receive/extract the bitstream and transmit it to the decoding device.

The decoding apparatus may decode the video/image by performing a series of procedures such as inverse quantization, inverse transformation, and prediction corresponding to the operation of the encoding apparatus.

The renderer may render the decoded video/image. The rendered video/image may be displayed through the display unit.

This article is about video/image coding. For example, the method/embodiment disclosed in this document is a versatile video coding (VVC) standard, an essential video coding (EVC) standard, an AOMedia Video 1 (AV1) standard, a 2nd generation of audio video coding standard (AVS2) or a next-generation video/ It can be applied to the method disclosed in the image coding standard (ex. H.267 or H.268, etc.).

This document presents various embodiments related to video/image coding, and unless otherwise stated, the embodiments may be combined with each other.

In this document, a video may mean a set of a series of images according to the passage of time. A picture generally refers to a unit representing one image in a specific time period, and a subpicture/slice/tile is a unit constituting a part of a picture in coding. A subpicture/slice/tile may include one or more coding tree units (CTUs). One picture may be composed of one or more subpictures/slice/tile. One picture may be composed of one or more tile groups. One tile group may include one or more tiles. A brick may indicate a rectangular area of CTU rows within a tile in a picture. A tile may be partitioned into multiple bricks, and each brick may consist of one or more CTU rows within the tile. A tile that is not partitioned into multiple bricks may also be referred to as a brick. A brick scan may indicate a specific sequential ordering of CTUs partitioning a picture, the CTUs may be arranged in a CTU raster scan within a brick, and the bricks in a tile may be sequentially arranged in a raster scan of the bricks of the tile. and tiles in a picture may be sequentially aligned with a raster scan of the tiles of the picture. In addition, a sub-picture may indicate a rectangular region of one or more slices in the picture. That is, the sub-picture may include one or more slices that collectively cover the rectangular area of the picture. A tile is a specific tile row and a rectangular area of CTUs within a specific tile row. The tile column is a rectangular region of CTUs, the rectangular region has a height equal to the height of the picture, and the width may be specified by syntax elements in a picture parameter set. The tile row is a rectangular region of CTUs, the rectangular region has a width specified by syntax elements in a picture parameter set, and the height may be equal to the height of the picture. A tile scan may indicate a specific sequential ordering of CTUs partitioning a picture, wherein the CTUs may be sequentially aligned with a CTU raster scan within a tile, and tiles within a picture may be sequentially aligned with a raster scan of the tiles of the picture. can A slice may include an integer number of bricks of a picture, and the integer number of bricks may be included in one NAL unit. A slice may consist of a number of complete tiles, or it may be a continuous sequence of complete bricks of one tile. In this document, tile group and slice can be used interchangeably. For example, in this document, a tile group/tile group header may be referred to as a slice/slice header.

A pixel or pel may mean a minimum unit constituting one picture (or image). Also, as a term corresponding to a pixel, a 'sample' may be used. The sample may generally represent a pixel or a value of a pixel, may represent only a pixel/pixel value of a luma component, or may represent only a pixel/pixel value of a chroma component.

A unit may represent a basic unit of image processing. The unit may include at least one of a specific region of a picture and information related to the region. One unit may include one luma block and two chroma (ex. cb, cr) blocks. A unit may be used interchangeably with terms such as a block or an area in some cases. In a general case, the MxN block may include samples (or sample arrays) or a set (or arrays) of transform coefficients including M columns and N rows.

In this specification, "A or B (A or B)" may mean "only A", "only B", or "both A and B". In other words, “A or B (A or B)” in the present specification may be interpreted as “A and/or B (A and/or B)”. For example, "A, B or C(A, B or C)" herein means "only A", "only B", "only C", or "any and any combination of A, B and C ( any combination of A, B and C)".

As used herein, a slash (/) or a comma (comma) may mean “and/or”. For example, “A/B” may mean “A and/or B”. Accordingly, “A/B” may mean “only A”, “only B”, or “both A and B”. For example, “A, B, C” may mean “A, B, or C”.

As used herein, “at least one of A and B” may mean “only A”, “only B” or “both A and B”. Also, in the present specification, the expression “at least one of A or B” or “at least one of A and/or B” means “at least one of A and/or B”. It can be interpreted the same as "A and B (at least one of A and B)".

Also, as used herein, "at least one of A, B and C" means "only A", "only B", "only C", or "A, B and C" any combination of A, B and C". Also, “at least one of A, B or C” or “at least one of A, B and/or C” means can mean "at least one of A, B and C".

In addition, parentheses used herein may mean "for example". Specifically, when “prediction (intra prediction)” is indicated, “intra prediction” may be proposed as an example of “prediction”. In other words, “prediction” in the present specification is not limited to “intra prediction”, and “intra prediction” may be proposed as an example of “prediction”. Also, even when “prediction (ie, intra prediction)” is indicated, “intra prediction” may be proposed as an example of “prediction”.

In this specification, technical features that are individually described within one drawing may be implemented individually or simultaneously.

The following drawings were created to explain a specific example of the present specification. Since the names of specific devices described in the drawings or the names of specific signals/messages/fields are presented by way of example, the technical features of the present specification are not limited to the specific names used in the following drawings.

2 is a diagram schematically illustrating a configuration of a video/image encoding apparatus to which embodiments of the present document may be applied. Hereinafter, a video encoding apparatus may include an image encoding apparatus.

2, the encoding apparatus 200 includes an image partitioner 210, a predictor 220, a residual processor 230, an entropy encoder 240, It may be configured to include an adder 250 , a filter 260 , and a memory 270 . The prediction unit 220 may include an inter prediction unit 221 and an intra prediction unit 222 . The residual processing unit 230 may include a transformer 232 , a quantizer 233 , an inverse quantizer 234 , and an inverse transformer 235 . The residual processing unit 230 may further include a subtractor 231 . The adder 250 may be referred to as a reconstructor or a reconstructed block generator. The above-described image segmentation unit 210, prediction unit 220, residual processing unit 230, entropy encoding unit 240, adder 250 and filtering unit 260 may include one or more hardware components ( For example, by an encoder chipset or processor). In addition, the memory 270 may include a decoded picture buffer (DPB), and may be configured by a digital storage medium. The hardware component may further include a memory 270 as an internal/external component.

The image dividing unit 210 may divide an input image (or a picture, a frame) input to the encoding apparatus 200 into one or more processing units. For example, the processing unit may be referred to as a coding unit (CU). In this case, the coding unit is to be recursively divided according to a quad-tree binary-tree ternary-tree (QTBTTT) structure from a coding tree unit (CTU) or largest coding unit (LCU). can For example, one coding unit may be divided into a plurality of coding units having a lower depth based on a quad tree structure, a binary tree structure, and/or a ternary structure. In this case, for example, a quad tree structure may be applied first and a binary tree structure and/or a ternary structure may be applied later. Alternatively, the binary tree structure may be applied first. A coding procedure according to this document may be performed based on the final coding unit that is no longer divided. In this case, the maximum coding unit may be directly used as the final coding unit based on coding efficiency according to image characteristics, or the coding unit may be recursively divided into coding units having a lower depth than the optimal coding unit if necessary. A coding unit of the size of may be used as the final coding unit. Here, the coding procedure may include procedures such as prediction, transformation, and restoration, which will be described later. As another example, the processing unit may further include a prediction unit (PU) or a transform unit (TU). In this case, the prediction unit and the transform unit may be divided or partitioned from the above-described final coding unit, respectively. The prediction unit may be a unit of sample prediction, and the transform unit may be a unit for deriving a transform coefficient and/or a unit for deriving a residual signal from the transform coefficient.

A unit may be used interchangeably with terms such as a block or an area in some cases. In general, an MxN block may represent a set of samples or transform coefficients including M columns and N rows. A sample may generally represent a pixel or a value of a pixel, may represent only a pixel/pixel value of a luma component, or may represent only a pixel/pixel value of a chroma component. A sample may be used as a term corresponding to a picture (or image) as a pixel or a pel.

The encoding apparatus 200 subtracts the prediction signal (predicted block, prediction sample array) output from the inter prediction unit 221 or the intra prediction unit 222 from the input image signal (original block, original sample array) to obtain a residual A signal (residual signal, residual block, residual sample array) may be generated, and the generated residual signal is transmitted to the converter 232 . In this case, as illustrated, a unit for subtracting a prediction signal (prediction block, prediction sample array) from an input image signal (original block, original sample array) in the encoder 200 may be referred to as a subtraction unit 231 . The prediction unit may perform prediction on a processing target block (hereinafter, referred to as a current block) and generate a predicted block including prediction samples for the current block. The prediction unit may determine whether intra prediction or inter prediction is applied on a current block or CU basis. The prediction unit may generate various information about prediction, such as prediction mode information, and transmit it to the entropy encoding unit 240 , as will be described later in the description of each prediction mode. The prediction information may be encoded by the entropy encoding unit 240 and output in the form of a bitstream.

The intra prediction unit 222 may predict the current block with reference to samples in the current picture. The referenced samples may be located in the neighborhood of the current block or may be located apart from each other according to the prediction mode. In intra prediction, prediction modes may include a plurality of non-directional modes and a plurality of directional modes. The non-directional mode may include, for example, a DC mode and a planar mode (Planar mode). The directional mode may include, for example, 33 directional prediction modes or 65 directional prediction modes according to the granularity of the prediction direction. However, this is an example, and a higher or lower number of directional prediction modes may be used according to a setting. The intra prediction unit 222 may determine the prediction mode applied to the current block by using the prediction mode applied to the neighboring block.

The inter prediction unit 221 may derive the predicted block for the current block based on the reference block (reference sample array) specified by the motion vector on the reference picture. In this case, in order to reduce the amount of motion information transmitted in the inter prediction mode, motion information may be predicted in units of blocks, subblocks, or samples based on the correlation between motion information between neighboring blocks and the current block. The motion information may include a motion vector and a reference picture index. The motion information may further include inter prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter prediction, the neighboring blocks may include spatial neighboring blocks existing in the current picture and temporal neighboring blocks present in the reference picture. The reference picture including the reference block and the reference picture including the temporal neighboring block may be the same or different. The temporal neighboring block may be called a collocated reference block, a collocated CU (colCU), etc., and a reference picture including the temporally neighboring block may be called a collocated picture (colPic). may be For example, the inter prediction unit 221 constructs a motion information candidate list based on neighboring blocks, and provides information indicating which candidate is used to derive a motion vector and/or a reference picture index of the current block. can create Inter prediction may be performed based on various prediction modes. For example, in the skip mode and merge mode, the inter prediction unit 221 may use motion information of a neighboring block as motion information of the current block. In the skip mode, unlike the merge mode, a residual signal may not be transmitted. In the case of motion vector prediction (MVP) mode, the motion vector of the current block is determined by using a motion vector of a neighboring block as a motion vector predictor and signaling a motion vector difference. can direct

The prediction unit 220 may generate a prediction signal based on various prediction methods to be described later. For example, the prediction unit may apply intra prediction or inter prediction for prediction of one block, and may simultaneously apply intra prediction and inter prediction. This can be called combined inter and intra prediction (CIIP). In addition, the prediction unit may be based on an intra block copy (IBC) prediction mode or based on a palette mode for prediction of a block. The IBC prediction mode or the palette mode may be used for video/video coding of content such as games, for example, screen content coding (SCC). IBC basically performs prediction within the current picture, but may be performed similarly to inter prediction in that a reference block is derived within the current picture. That is, IBC may use at least one of the inter prediction techniques described in this document. The palette mode may be viewed as an example of intra coding or intra prediction. When the palette mode is applied, the sample value in the picture may be signaled based on information about the palette table and palette index.

The prediction signal generated by the prediction unit (including the inter prediction unit 221 and/or the intra prediction unit 222 ) may be used to generate a reconstructed signal or may be used to generate a residual signal. The transform unit 232 may generate transform coefficients by applying a transform technique to the residual signal. For example, the transformation method may include at least one of Discrete Cosine Transform (DCT), Discrete Sine Transform (DST), Karhunen-Loeve Transform (KLT), Graph-Based Transform (GBT), or Conditionally Non-linear Transform (CNT). may include Here, GBT means a transformation obtained from this graph when expressing relationship information between pixels in a graph. CNT refers to a transformation obtained by generating a prediction signal using all previously reconstructed pixels and based thereon. In addition, the transformation process may be applied to a block of pixels having the same size as a square, or may be applied to a block of a variable size that is not a square.

The quantization unit 233 quantizes the transform coefficients and transmits them to the entropy encoding unit 240, and the entropy encoding unit 240 encodes the quantized signal (information on the quantized transform coefficients) and outputs it as a bitstream. have. Information about the quantized transform coefficients may be referred to as residual information. The quantization unit 233 may rearrange the quantized transform coefficients in the block form into a one-dimensional vector form based on a coefficient scan order, and the quantized transform coefficients in the one-dimensional vector form are quantized based on the quantized transform coefficients in the one-dimensional vector form. Information about the transform coefficients may be generated. The entropy encoding unit 240 may perform various encoding methods such as, for example, exponential Golomb, context-adaptive variable length coding (CAVLC), and context-adaptive binary arithmetic coding (CABAC). The entropy encoding unit 240 may encode information necessary for video/image reconstruction (eg, values of syntax elements, etc.) other than the quantized transform coefficients together or separately. Encoded information (eg, encoded video/image information) may be transmitted or stored in a network abstraction layer (NAL) unit unit in the form of a bitstream. The video/image information may further include information about various parameter sets, such as an adaptation parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). Also, the video/image information may further include general constraint information. In this document, information and/or syntax elements transmitted/signaled from the encoding device to the decoding device may be included in video/image information. The video/image information may be encoded through the above-described encoding procedure and included in the bitstream. The bitstream may be transmitted over a network or may be stored in a digital storage medium. Here, the network may include a broadcasting network and/or a communication network, and the digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, and SSD. In the signal output from the entropy encoding unit 240, a transmitting unit (not shown) and/or a storing unit (not shown) for storing may be configured as internal/external elements of the encoding apparatus 200, or the transmitting unit It may be included in the entropy encoding unit 240 .

The quantized transform coefficients output from the quantization unit 233 may be used to generate a prediction signal. For example, the residual signal (residual block or residual samples) may be reconstructed by applying inverse quantization and inverse transform to the quantized transform coefficients through the inverse quantizer 234 and the inverse transform unit 235 . The adder 250 adds the reconstructed residual signal to the prediction signal output from the inter prediction unit 221 or the intra prediction unit 222 to obtain a reconstructed signal (reconstructed picture, reconstructed block, reconstructed sample array). can be created When there is no residual for the block to be processed, such as when the skip mode is applied, the predicted block may be used as a reconstructed block. The adder 250 may be referred to as a restoration unit or a restoration block generator. The generated reconstructed signal may be used for intra prediction of the next processing object block in the current picture, or may be used for inter prediction of the next picture after filtering as described below.

Meanwhile, luma mapping with chroma scaling (LMCS) may be applied during picture encoding and/or restoration.

The filtering unit 260 may improve subjective/objective image quality by applying filtering to the reconstructed signal. For example, the filtering unit 260 may generate a modified reconstructed picture by applying various filtering methods to the reconstructed picture, and convert the modified reconstructed picture to the memory 270 , specifically the DPB of the memory 270 . can be stored in The various filtering methods may include, for example, deblocking filtering, a sample adaptive offset, an adaptive loop filter, a bilateral filter, and the like. The filtering unit 260 may generate various types of filtering-related information and transmit it to the entropy encoding unit 240 , as will be described later in the description of each filtering method. The filtering-related information may be encoded by the entropy encoding unit 240 and output in the form of a bitstream.

The modified reconstructed picture transmitted to the memory 270 may be used as a reference picture in the inter prediction unit 221 . When inter prediction is applied through this, the encoding apparatus can avoid prediction mismatch between the encoding apparatus 200 and the decoding apparatus 300 and improve encoding efficiency.

The memory 270 DPB may store the corrected reconstructed picture to be used as a reference picture in the inter prediction unit 221 . The memory 270 may store motion information of a block in which motion information in the current picture is derived (or encoded) and/or motion information of blocks in an already reconstructed picture. The stored motion information may be transmitted to the inter prediction unit 221 to be used as motion information of a spatial neighboring block or motion information of a temporal neighboring block. The memory 270 may store reconstructed samples of blocks reconstructed in the current picture, and may transmit the reconstructed samples to the intra prediction unit 222 .

3 is a diagram schematically illustrating a configuration of a video/image decoding apparatus to which embodiments of the present document may be applied.

Referring to FIG. 3 , the decoding apparatus 300 includes an entropy decoder 310 , a residual processor 320 , a predictor 330 , an adder 340 , and a filtering unit. (filter, 350) and may be configured to include a memory (memory, 360). The prediction unit 330 may include an inter prediction unit 331 and an intra prediction unit 332 . The residual processing unit 320 may include a dequantizer 321 and an inverse transformer 322 . The entropy decoding unit 310 , the residual processing unit 320 , the prediction unit 330 , the addition unit 340 , and the filtering unit 350 are one hardware component (eg, a decoder chipset or a processor according to an embodiment). ) can be configured by In addition, the memory 360 may include a decoded picture buffer (DPB), and may be configured by a digital storage medium. The hardware component may further include a memory 360 as an internal/external component.

When a bitstream including video/image information is input, the decoding apparatus 300 may reconstruct an image corresponding to a process in which the video/image information is processed in the encoding apparatus of FIG. 2 . For example, the decoding apparatus 300 may derive units/blocks based on block division related information obtained from the bitstream. The decoding apparatus 300 may perform decoding by using a processing unit applied in the encoding apparatus. Thus, the processing unit of decoding may be, for example, a coding unit, and the coding unit may be divided according to a quad tree structure, a binary tree structure and/or a ternary tree structure from a coding tree unit or a largest coding unit. One or more transform units may be derived from a coding unit. In addition, the reconstructed image signal decoded and output through the decoding apparatus 300 may be reproduced through the reproducing apparatus.

The decoding apparatus 300 may receive a signal output from the encoding apparatus of FIG. 2 in the form of a bitstream, and the received signal may be decoded through the entropy decoding unit 310 . For example, the entropy decoding unit 310 may parse the bitstream to derive information (eg, video/image information) required for image restoration (or picture restoration). The video/image information may further include information about various parameter sets, such as an adaptation parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS). Also, the video/image information may further include general constraint information. The decoding apparatus may decode the picture further based on the information on the parameter set and/or the general restriction information. Signaled/received information and/or syntax elements described later in this document may be decoded through the decoding procedure and obtained from the bitstream. For example, the entropy decoding unit 310 decodes information in a bitstream based on a coding method such as exponential Golomb encoding, CAVLC or CABAC, and a value of a syntax element required for image reconstruction and a quantized value of a transform coefficient related to a residual can be printed out. In more detail, the CABAC entropy decoding method receives a bin corresponding to each syntax element in a bitstream, and decodes the syntax element information to be decoded and the decoding information of the surrounding and decoding target blocks or the symbol/bin information decoded in the previous step. A context model is determined using the context model, and the probability of occurrence of a bin is predicted according to the determined context model, and a symbol corresponding to the value of each syntax element can be generated by performing arithmetic decoding of the bin. have. In this case, the CABAC entropy decoding method may update the context model by using the decoded symbol/bin information for the context model of the next symbol/bin after determining the context model. Prediction-related information among the information decoded by the entropy decoding unit 310 is provided to the prediction unit (the inter prediction unit 332 and the intra prediction unit 331), and the entropy decoding unit 310 performs entropy decoding. Dual values, that is, quantized transform coefficients and related parameter information may be input to the residual processing unit 320 . The residual processing unit 320 may derive a residual signal (residual block, residual samples, residual sample array). Also, information on filtering among the information decoded by the entropy decoding unit 310 may be provided to the filtering unit 350 . On the other hand, a receiving unit (not shown) that receives a signal output from the encoding device may be further configured as an internal/external element of the decoding device 300 , or the receiving unit may be a component of the entropy decoding unit 310 . On the other hand, the decoding apparatus according to this document may be called a video/image/picture decoding apparatus, and the decoding apparatus is divided into an information decoder (video/image/picture information decoder) and a sample decoder (video/image/picture sample decoder). may be The information decoder may include the entropy decoding unit 310 , and the sample decoder includes the inverse quantization unit 321 , the inverse transform unit 322 , the adder 340 , the filtering unit 350 , and the memory 360 . ), an inter prediction unit 332 , and an intra prediction unit 331 .

The inverse quantizer 321 may inverse quantize the quantized transform coefficients to output transform coefficients. The inverse quantizer 321 may rearrange the quantized transform coefficients in a two-dimensional block form. In this case, the rearrangement may be performed based on the coefficient scan order performed by the encoding device. The inverse quantizer 321 may perform inverse quantization on the quantized transform coefficients using a quantization parameter (eg, quantization step size information) and obtain transform coefficients.

The inverse transform unit 322 inverse transforms the transform coefficients to obtain a residual signal (residual block, residual sample array).

The prediction unit may perform prediction on the current block and generate a predicted block including prediction samples for the current block. The prediction unit may determine whether intra prediction or inter prediction is applied to the current block based on the prediction information output from the entropy decoding unit 310 , and may determine a specific intra/inter prediction mode.

The prediction unit 320 may generate a prediction signal based on various prediction methods to be described later. For example, the prediction unit may apply intra prediction or inter prediction for prediction of one block, and may simultaneously apply intra prediction and inter prediction. This can be called combined inter and intra prediction (CIIP). In addition, the prediction unit may be based on an intra block copy (IBC) prediction mode or based on a palette mode for prediction of a block. The IBC prediction mode or the palette mode may be used for video/video coding of content such as games, for example, screen content coding (SCC). IBC basically performs prediction within the current picture, but may be performed similarly to inter prediction in that a reference block is derived within the current picture. That is, IBC may use at least one of the inter prediction techniques described in this document. The palette mode may be viewed as an example of intra coding or intra prediction. When the palette mode is applied, information about the palette table and the palette index may be included in the video/image information and signaled.

The intra prediction unit 331 may predict the current block with reference to samples in the current picture. The referenced samples may be located in the neighborhood of the current block or may be located apart from each other according to the prediction mode. In intra prediction, prediction modes may include a plurality of non-directional modes and a plurality of directional modes. The intra prediction unit 331 may determine the prediction mode applied to the current block by using the prediction mode applied to the neighboring block.

The inter prediction unit 332 may derive the predicted block for the current block based on the reference block (reference sample array) specified by the motion vector on the reference picture. In this case, in order to reduce the amount of motion information transmitted in the inter prediction mode, motion information may be predicted in units of blocks, subblocks, or samples based on the correlation between motion information between neighboring blocks and the current block. The motion information may include a motion vector and a reference picture index. The motion information may further include inter prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information. In the case of inter prediction, the neighboring blocks may include spatial neighboring blocks existing in the current picture and temporal neighboring blocks present in the reference picture. For example, the inter prediction unit 332 may construct a motion information candidate list based on neighboring blocks, and derive a motion vector and/or a reference picture index of the current block based on the received candidate selection information. Inter prediction may be performed based on various prediction modes, and the prediction information may include information indicating a mode of inter prediction for the current block.

The adder 340 restores the obtained residual signal by adding it to the prediction signal (predicted block, prediction sample array) output from the prediction unit (including the inter prediction unit 332 and/or the intra prediction unit 331 ). A signal (reconstructed picture, reconstructed block, reconstructed sample array) may be generated. When there is no residual for the block to be processed, such as when the skip mode is applied, the predicted block may be used as a reconstructed block.

The adder 340 may be referred to as a restoration unit or a restoration block generator. The generated reconstructed signal may be used for intra prediction of the next processing object block in the current picture, may be output through filtering as described below, or may be used for inter prediction of the next picture.

Meanwhile, luma mapping with chroma scaling (LMCS) may be applied in the picture decoding process.

The filtering unit 350 may improve subjective/objective image quality by applying filtering to the reconstructed signal. For example, the filtering unit 350 may generate a modified reconstructed picture by applying various filtering methods to the reconstructed picture, and store the modified reconstructed picture in the memory 360 , specifically, the DPB of the memory 360 . can be sent to The various filtering methods may include, for example, deblocking filtering, a sample adaptive offset, an adaptive loop filter, a bilateral filter, and the like.

The (modified) reconstructed picture stored in the DPB of the memory 360 may be used as a reference picture in the inter prediction unit 332 . The memory 360 may store motion information of a block from which motion information in the current picture is derived (or decoded) and/or motion information of blocks in an already reconstructed picture. The stored motion information may be transmitted to the inter prediction unit 260 to be used as motion information of a spatial neighboring block or motion information of a temporal neighboring block. The memory 360 may store reconstructed samples of blocks reconstructed in the current picture, and may transmit the reconstructed samples to the intra prediction unit 331 .

In this specification, the embodiments described in the filtering unit 260 , the inter prediction unit 221 , and the intra prediction unit 222 of the encoding apparatus 200 are the filtering unit 350 and the inter prediction unit of the decoding apparatus 300 , respectively. The same or corresponding application may be applied to the unit 332 and the intra prediction unit 331 .

In this document, at least one of quantization/inverse quantization and/or transform/inverse transform may be omitted. When the quantization/inverse quantization is omitted, the quantized transform coefficient may be referred to as a transform coefficient. When the transform/inverse transform is omitted, the transform coefficients may be called coefficients or residual coefficients, or may still be called transform coefficients for uniformity of expression.

In this document, a quantized transform coefficient and a transform coefficient may be referred to as a transform coefficient and a scaled transform coefficient, respectively. In this case, the residual information may include information on transform coefficient(s), and the information on the transform coefficient(s) may be signaled through residual coding syntax. Transform coefficients may be derived based on the residual information (or information about the transform coefficient(s)), and scaled transform coefficients may be derived through inverse transform (scaling) on the transform coefficients. Residual samples may be derived based on an inverse transform (transform) of the scaled transform coefficients. This may be applied/expressed in other parts of this document as well.

Meanwhile, the video/image information may include information on a decoded picture buffer (DPB) of an output layer set (OLS) and/or information on a hypothetical reference decoder (HRD). For example, the video/image information may include a video parameter set (VPS), and the VPS is a parameter set used to transmit information on the DPB and/or information on the HRD. can

For example, the information on the DPB and/or the information on the HRD may be signaled for each OLS. Here, the HRD is a conforming network abstraction layer (NAL) unit stream that can be generated by the encoding process (conforming NAL unit streams) or conforming byte streams (constraints) on the variability of the It may be a hypothetical decoder model. When the HRD exists, information on the HRD may be included in a VPS or a sequence parameter set (SPS) as follows. In addition, the information on the DPB may be included in a VPS or a sequence parameter set (SPS) as follows.

For example, Table 1 described above may indicate a Video Parameter Set (VPS) including syntax elements for a signaled DPB parameter and/or syntax elements for an HRD parameter.

Semantics of the syntax elements shown in Table 1 above may be as follows.

For example, the variable NumLayersInOls[i] the variable NumLayersInOls[i] specifying the number of layers in the i-th OLS, the variable LayerIdInOls[i][j] specifying the value of the nuh_layer_id of the j-th layer within the i-th OLS, and the multi-layer ( A variable NumMultiLayerOlss that specifies the number of multi-layer) OLSs (ie, OLSs including two or more layers) may be derived as shown in Table 2 above.

Also, for example, referring to Table 3, when the syntax element vps_num_dpb_params_minus1 exists, the syntax element vps_num_dpb_params_minus1 may indicate the number of dpb_parameters() syntax structures of the VPS. The value of vps_num_dpb_params_minus1 may range from 0 to NumMultiLayerOlss - 1.

For example, the variable VpsNumDpbParams indicating the number of dpb_parameters() syntax structures of the VPS may be derived as 0 when the value of vps_each_layer_is_an_ols_flag is 1, and may be derived as vps_each_layer_is_an_ols_flag as Vps_min_dups_min. .

Also, for example, the syntax element vps_sublayer_dpb_params_present_flag may be used to control the presence of syntax elements max_dec_pic_buffering_minus1[], max_num_reorder_pics[] and max_latency_increase_plus1[] in the dpb_parameters() syntax structure of the VPS. In addition, when the syntax element vps_sublayer_dpb_params_present_flag does not exist, the value of the syntax element vps_sublayer_dpb_params_present_flag may be considered equal to 0.

Also, for example, the syntax element vps_dpb_max_temporal_id[i] may indicate the TemporalId of the highest sublayer representation in which the DPB parameter may exist in the i-th dpb_parameters() syntax structure in the VPS. Also, the value of vps_dpb_max_temporal_id[i] may be in the range of 0 to vps_max_sublayers_minus1. Also, for example, when the syntax element vps_dpb_max_temporal_id[i] does not exist, the value of vps_dpb_max_temporal_id[i] may be considered to be equal to vps_max_sublayers_minus1.

Also, for example, the syntax element vps_ols_dpb_pic_width[i] may indicate, in units of luma samples, the width of each picture storage buffer for the i-th OLS.

Also, for example, the syntax element vps_ols_dpb_pic_height[i] may indicate, in units of luma samples, the height of each picture storage buffer for the i-th OLS.

Also, for example, the syntax element vps_ols_dpb_chroma_format[i] may indicate the maximum allowable value of sps_chroma_format_idc for all SPSs referenced by the CLVS of the CVS for the i-th OLS.

Also, for example, the syntax element vps_ols_dpb_bitdepth_minus8[i] may indicate the maximum allowable value of sps_bit_depth_minus8 for all SPSs referenced by the CLVS of the CVS for the i-th OLS.

Also, for example, the syntax element vps_ols_dpb_params_idx[i] may indicate an index of a dpb_parameters() syntax structure applied to the i-th OLS. The index may be an index of the dpb_parameters() syntax structure list of the VPS. That is, the syntax element vps_ols_dpb_params_idx[i] may indicate an index of a dpb_parameters() syntax structure applied to the i-th OLS among a plurality of dpb_parameters() syntax structures of the VPS. The value of vps_ols_dpb_params_idx[i] may be in the range of 0 to VpsNumDpbParams-1.

Here, when the syntax element vps_ols_dpb_params_idx[i] does not exist, the value of the syntax element vps_ols_dpb_params_idx[i] may be regarded as follows. For example, if VpsNumDpbParams is 1, the value of vps_ols_dpb_params_idx[i] may be inferred to be equal to 0, otherwise (i.e., if VpsNumDpbParams is greater than 1 and equal to NumMultiLayerOlss), the value of vps_ols_idx[i] can be considered equal to i (inferred).

Also, for example, for a single-layer OLS, an applicable dpb_parameters() syntax structure may exist in the SPS referenced by the layer of the OLS. Each dpb_parameters() syntax structure of the VPS may be referenced as at least one value of vps_ols_dpb_params_idx[i] for i within the range of 0 to NumMultiLayerOlss-1.

Also, for example, the syntax element vps_general_hrd_params_present_flag may indicate whether the VPS includes a general_hrd_parameters() syntax structure and other HRD parameters. For example, vps_general_hrd_params_present_flag equal to 1 may indicate that the VPS includes the general_hrd_parameters() syntax structure and other HRD parameters, and vps_general_hrd_params_present_flag equal to 0 indicates that the VPS includes general_hrd_parameters() syntax structure and other HRD parameters. other HRD parameters). When the syntax element vps_general_hrd_params_present_flag does not exist, the value of the syntax element vps_general_hrd_params_present_flag may be inferred to be equal to 0.

When NumLayersInOls[i] is 1, the general_hrd_parameters() syntax structure and the ols_hrd_parameters() syntax structure applied to the i-th OLS may exist in the SPS referenced by the i-th OLS layer.

Also, for example, the syntax element vps_sublayer_cpb_params_present_flag indicates whether an HRD parameter for sublayer representations with a TemporalId range of 0 to hrd_max_tid[i] (inclusive) is included in the i-th ols_hrd_parameters() syntax structure of the VPS. can For example, vps_sublayer_cpb_params_present_flag equal to 1 may indicate that the i-th ols_hrd_parameters() syntax structure of the VPS includes HRD parameters for sublayer representations whose TemporalId ranges from 0 to hrd_max_tid[i] (inclusive), vps_sublayer_cpb_params_present_flag equal to 0 may indicate that TemporalId includes only HRD parameters for sublayer representation such as hrd_max_tid[i] in the i-th ols_hrd_parameters() syntax structure of VPS. When vps_max_sublayers_minus1 is 0, the value of vps_sublayer_cpb_params_present_flag may be considered equal to 0.

If vps_sublayer_cpb_params_present_flag is 0, HRD parameters for sublayer representations with TemporalId ranging from 0 to hrd_max_tid[i] (inclusive) are considered equal to HRD parameters for sublayer representations with TemporalId equal to hrd_max_tid[i] can be Here, HRD parameters may be included from the syntax element fixed_pic_rate_general_flag[i] to the sublayer_hrd_parameters(i) syntax structure immediately below the condition "if (general_vcl_hrd_params_present_flag)" of the ols_hrd_parameters syntax structure.

Also, for example, the syntax element vps_num_ols_hrd_params_minus1+1 may indicate the number of ols_hrd_parameters() syntax structures present in the VPS when vps_general_hrd_params_present_flag is 1. The value of num_ols_hrd_params_minus1 may range from 0 to TotalNumOlss-1.

Also, for example, the syntax element hrd_max_tid[i] may indicate the TemporalId of the highest sub-layer expression for the HRD parameter included in the i-th ols_hrd_parameters() syntax structure. The value of hrd_max_tid[i] may range from 0 to vps_max_sublayers_minus1. When vps_max_sublayers_minus1 is 0, the value of hrd_max_tid[i] may be regarded as 0. When the syntax element hrd_max_tid[i] does not exist, the value of the syntax element hrd_max_tid[i] may be considered equal to vps_max_sublayers_minus1.

Also, for example, the syntax element vps_ols_hrd_idx[i] may indicate an index of the ols_hrd_parameters() syntax structure applied to the i-th multi-layer OLS. The index may be an index of the ols_hrd_parameters() syntax structure list of the VPS. That is, the syntax element ols_hrd_idx[i] may indicate an index of an ols_hrd_parameters() syntax structure applied to the i-th multi-layer OLS among a plurality of ols_hrd_parameters() syntax structures of the VPS. Here, the value of ols_hrd_idx[i] may be in the range of 0 to vps_num_ols_hrd_params_minus1.

If NumLayersInOls[i] is greater than 1 and vps_ols_hrd_idx[i] does not exist, it can be considered as For example, if vps_num_ols_hrd_params_minus1 is 0, then the value of vps_ols_hrd_idx[i] can be considered equal to 0; The value can be considered equal to i.

Meanwhile, for a single-layer OLS (that is, when NumLayersInOls[i] is 1), the ols_hrd_parameters() syntax structure applied to the i-th OLS may exist in the SPS referenced by the i-th OLS layer.

Each ols_hrd_parameters() syntax structure of the VPS may be referred to as at least one value of vps_ols_hrd_idx[i] for i in the range of 1 to NumMultiLayerOlss-1.

As described above, DPB-related information and/or HRD-related information may be signaled. On the other hand, vps_ols_dpb_pic_width[i], vps_ols_dpb_pic_height[i], vps_ols_dpb_chroma_format[i], vps_ols_dpb_bitdepth_minus8[i], vps_ols_dpb_params_idx[i] according to the existing video/video standard can have the same problems as the following signaling methods and vps_ols_dpb_params_idx[i], vps signaling methods. .

Specifically, the above-described syntax elements may be signaled only for OLS with multi-layers. However, when the above-described syntax elements are referenced in the decoding process, an index for a target OLS index (ie, an index of the OLS to be decoded) may refer to all OLS lists. That is, the indices of the above-described syntax elements to the target OLS may refer to all OLSs including the multi-layer OLS and the single-layer OLS.

The above-described mismatch of the index for the target OLS may cause the decoding apparatus to point to the wrong DPB information and HRD information set when the target OLS is an OLS having multi-layers. In other words, although the above-described syntax elements are signaled only for the OLS including the multilayer, the target OLS index of the above-described syntax elements is set as an index for all OLSs including the OLS including the single layer, so that the decoding apparatus is the target It is possible to point to incorrect DPB-related information and HRD-related information rather than DPB-related information and HRD-related information for OLS as information about the target OLS.

Accordingly, this document proposes a solution to the above-described problem. The proposed embodiments may be applied individually or in combination.

As an example, a mapping in a list of all OLSs signaled by the VPS and a list of OLSs in which the number of layers is greater than 1 may be defined. That is, for example, a mapping between a list of all OLSs signaled in the VPS and a list of OLSs in which the number of layers is greater than 1 may be defined. An OLS in which the number of layers is greater than 1 may be referred to as a multi-layer OLS.

Specifically, for example, a) the mapping should be such that an index can be converted into a list of all OLSs from a list of OLSs having multi-layers to an index of the same OLS. In other words, the mapping should convert the index of the target OLS in the list of all OLSs into the index of the target OLS in the list of OLSs having multilayers.

For example, b) the array mapping the two lists described above may be called MultiLayeredOlsIdx[i] for i ranges of 0 to OLS number minus 1. The value of MultiLayeredOlsIdx[i] may indicate the association between the i-th OLS (ie, all OLSs) and the j-th multilayer OLS, where j is the same as MultiLayeredOlsIdx[i].

As an example, the above-described array MultiLayeredOlsIdx[i] is the value of vps_ols_dpb_pic_width[j], vps_ols_dpb_pic_height[j], vps_ols_dpb_chroma_format[j], vhr_bit_jparas_min_depth corresponding values) can be used.

For example, the steps described below may be applied to embodiments of the present document. That is, the steps to be described below may be used to exemplarily describe the above embodiments.

For example, the encoding apparatus may derive information related to OLS. For example, the encoding apparatus may derive the HRD parameter and/or the DPB parameter. The OLS-related information may include HRD parameter-related information (ie, OLS HRD information) and/or DPB parameter-related information (ie, OLS DPB information). The encoding apparatus may encode picture(s) based on the OLS-related information. The encoding apparatus may encode the picture(s) based on at least one of an HRD parameter and/or a DPB parameter. Thereafter, the encoding apparatus may encode video/image information including the OLS-related information and output a bitstream. For example, the encoding apparatus may encode video/image information including HRD parameter related information and/or DPB parameter related information, and output a bitstream. Here, the bitstream may be a multi-layer bitstream. That is, the bitstream may include at least one sub-bitstream. An encoding process for OLS-related information (or HRD parameter-related information and/or DPB parameter-related information) may be performed based on the embodiment(s) of this document.

Also, for example, the decoding apparatus may derive video/image information from the bitstream. The bitstream may include at least one sub-bitstream. The sub-bitstream may be for a layer or OLS. For example, in a sub-bitstream extraction process, the NAL unit of the bitstream that does not belong to the target set determined by the target OLS index and the target highest TemporalId (target highest TemporalId) is the target set. It may be a designated process that is removed together with an output sub-bitstream composed of NAL units of a bitstream belonging to . The video/image information may include OLS-related information. Also, for example, the OLS related information may include HRD parameter related information and/or DPB parameter related information. The decoding apparatus may decode/output picture(s) based on the OLS-related information. For example, the coding apparatus may decode/output the picture(s) based on at least one of information related to an HRD parameter and/or information related to a DPB parameter. That is, for example, the decoding apparatus may decode or output the picture(s) based on OLS/DPB/HRD.

The above-described embodiments may be implemented as follows. For example, the above-described embodiments may be represented based on the VVC standard specification as described later.

Table 4 may show a process of deriving the multilayer OLS index (MultiLayeredOlsIdx[i]) of the i-th OLS.

For example, referring to Table 4, when the i-th OLS includes more than one layer (that is, when NumLayersInOls[i]>1), MultiLayeredOlsIdx[i] may be derived as NumMultiLayerOlss, and then The value of NumMultiLayerOlss may be incremented by one. That is, MultiLayeredOlsIdx[] for the multilayer OLS in the order after the i-th OLS may be derived as a value larger than MultiLayeredOlsIdx[i] for the i-th OLS.

Specifically, for example, when the target OLS is the nth OLS among multilayer OLSs, the multilayer OLS index of the target OLS may be derived as n-1. For example, when the target OLS, which is the i-th OLS among all OLSs, is the n-th OLS among the multi-layer OLSs, the multilayer OLS index (MultiLayeredOlsIdx[i]) of the target OLS can be derived as n-1. have.

Also, for example, referring to Table 5, a DPB parameter and/or an HRD parameter for the target OLS may be derived using MultiLayeredOlsIdx[TargetOlsIdx] for the target OLS.

For example, referring to Table 5, when the number of layers for the target OLS is greater than 1 (NumLayersInOls[TargetOlsIdx] is greater than 1), that is, when the target OLS is a multilayer OLS, the variable PicWidthMaxInSamplesY is vps_ols_dpb_pic_width[MultiLayeredOlsIdx [TargetOlsIdx]] may be set equal to, the variable PicHeightMaxInSamplesY may be set equal to vps_ols_dpb_pic_height[MultiLayeredOlsIdx[TargetOlsIdx]], and the variable PicSizeMaxInSamplesY applicable to PicWidthMaxHeightMaxInSamplesY may be set equal to PicWidthMaxHeightMaxInSamplesY* The dpb_parameters() syntax structure may be identified as vps_ols_dpb_params_idx[MultiLayeredOlsIdx[TargetOlsIdx]] in the VPS.

In addition, for example, referring to Table 5, when the number of layers for the target OLS is not 1 (NumLayersInOls[TargetOlsIdx] is not 1), that is, when the target OLS is a multi-layer OLS, general_hrd_parameters ( ) syntax structure and the vps_ols_hrd_idx[MultiLayeredOlsIdx[TargetOlsIdx]]-th ols_hrd_parameters() syntax structure may be selected as a general_hrd_parameters() syntax structure applicable to BitstreamToDecode, ols_hrd_parameters() syntax structure.

Also, for example, referring to Table 5, when the number of layers for the target OLS is greater than 1 (NumLayersInOls[TargetOlsIdx] is greater than 1), that is, when the target OLS is a multi-layer OLS, it is applied to the target OLS. dpb_parameters () syntax structure can be identified by vps_ols_dpb_params_idx [MultiLayeredOlsIdx [TargetOlsIdx]] in the VPS, variables PicWidthMaxInSamplesY, PicHeightMaxInSamplesY, MaxChromaFormat and MaxBitDepthMinus8 is vps_ols_dpb_pic_width [MultiLayeredOlsIdx [TargetOlsIdx]] in the VPS, respectively, vps_ols_dpb_pic_height [MultiLayeredOlsIdx [TargetOlsIdx ]], vps_ols_dpb_chroma_format[MultiLayeredOlsIdx[TargetOlsIdx]] and vps_ols_dpb_bitdepth_minus8[MultiLayeredOlsIdx[TargetOlsIdx]].

In addition, for example, referring to Table 5, when VCL HRD parameters or NAL HRD parameters exist, ols_hrd_parameters() syntax structures and all referenced VPS NAL units in all SPS NAL units referenced by the i-th layer The values of cpb_size_value_minus1[tIdTarget][j] of cpb_size_value_minus1[tIdTarget][j] of the j-th CPB of the vps_ols_hrd_idx[MultiLayeredOlsIdx[targetOlsIdx]]-th entry in the list of ols_hrd_parameters() syntax structures in (referenced VPS NAL units) are respectively SubpicCpbSizeVcl[SubpicSetLevelIdx][subpicIdx] and SubpicCpbSizeNal[SubpicSetLevelIdx][subpicIdx] derived by Equation D.6 and SubpicBitrateVcl[SubpicSetLevelIdx][subpicBitrateNal[SubpicSetLevelIdx][subpicBitrateVcl[SubpicSetLevelIdx] derived by Equation D.7 and D.8, respectively SubpicSetLevelIdx][subpicIdx] can be rewritten to be equivalent. Here, SubpicSetLevelIdx may be derived by Equation D.10 for a subpicture having the same subpicture index as subpicIdx, j may be in the range from 0 to hrd_cpb_cnt_minus1, and i may be in the range from 0 to NumLayersInOls [targetOlsIdx]-1 may be in range. Meanwhile, Equations D.5, D.6, D.7, D.8, and D.10 may be as disclosed in the VVC standard.

Also, for example, referring to Table 5, when sli_cbr_constraint_flag is 1, all NAL units having nal_unit_type of FD_NUT and filler payload SEI messages not associated with the VCL NAL units of the sub picture in subpicIdTarget[] will be removed. and may set the j-th CPB cbr_flag[tIdTarget][j] of the vps_ols_hrd_idx[MultiLayeredOlsIdx[targetOlsIdx]]-th entry in the list of ols_hrd_parameters() syntax structures of all referenced VPS NAL units and SPS NAL units. Here, j may be in the range of 0 to hrd_cpb_cnt_minus1. Also, otherwise, that is, when sli_cbr_constraint_flag is 0, nal_unit_type may remove all NAL units such as FD_NUT and filler payload SEI messages, and cbr_flag[tIdTarget][j] may be set to 0.

4 schematically illustrates an image encoding method by an encoding apparatus according to the present document. The method disclosed in FIG. 4 may be performed by the encoding apparatus disclosed in FIG. 2 . Specifically, for example, steps S400 to S420 of FIG. 4 may be performed by the entropy encoding unit of the encoding apparatus. Also, although not shown, the process of performing the DPB management process may be performed by the DPB of the encoding apparatus, and the process of decoding the current picture may be performed by the prediction unit and the residual processing unit of the encoding apparatus. .

The encoding apparatus derives the multi-layer OLS index of the target OLS in the list of multi-layer output layer sets (OLS) (S400). The encoding apparatus may derive the multilayer OLS index of the target OLS in the list of multilayer OLSs. Here, for example, the multi-layer OLSs may be OLSs including a plurality of layers. Also, for example, the target OLS may be one of the multi-layer OLSs.

For example, the encoding apparatus may derive the multi-layer OLS index as shown in Table 4 above. For example, when the target OLS is the nth OLS among multilayer OLSs, the multilayer OLS index of the target OLS may be derived as n-1. For example, when the target OLS, which is the i-th OLS among all OLSs, is the n-th OLS among the multi-layer OLSs, the multilayer OLS index (MultiLayeredOlsIdx[i]) of the target OLS can be derived as n-1. have.

The encoding apparatus generates Hypothetical Reference Decoder (HRD) related information and Decoded Picture Buffer (DPB) related information for the target OLS based on the multi-layer OLS index (S410). The encoding apparatus may decode/encode a picture in the target OLS, and may derive an HRD parameter and/or a DPB parameter for the target OLS. Also, the encoding apparatus may generate and encode the HRD-related information for the HRD parameter and/or the DPB-related information for the DPB parameter. For example, the encoding apparatus may derive the HRD parameter and/or the DPB parameter for a DPB management process.

For example, HRD-related information and / or the DPB related information vps_ols_dpb_pic_width [MultiLayeredOlsIdx [TargetOlsIdx]], vps_ols_dpb_pic_height [MultiLayeredOlsIdx [TargetOlsIdx]], vps_ols_dpb_chroma_format [MultiLayeredOlsIdx [TargetOlsIdx]], vps_ols_dpb_bitdepth_minus8 [MultiLayeredOlsIdx [TargetOlsIdx]], vps_ols_dpb_params_idx [MultiLayeredOlsIdx [ TargetOlsIdx]] and/or vps_ols_hrd_idx[MultiLayeredOlsIdx[TargetOlsIdx]].

For example, the HRD-related information may include an HRD index for an HRD parameter syntax structure of the target OLS. The HRD parameter syntax structure may be a syntax structure for the HRD parameter of the target OLS. The HRD index may be an HRD index for the multi-layer index. For example, the HRD index may indicate an HRD parameter syntax structure of the target OLS. The syntax element of the HRD index may be the aforementioned vps_ols_hrd_idx[MultiLayeredOlsIdx[TargetOlsIdx]].

For example, the encoding apparatus may generate the HRD parameter syntax structure of the target OLS, and may generate the HRD index indicating the HRD parameter syntax structure of the target OLS.

Also, for example, the DPB-related information includes a syntax element for the width of a decoded picture buffer (DPB) for the target OLS, a syntax element for the height of the DPB, and a chroma format of the DPB. It may include a syntax element for the DPB, a syntax element for the bit depth of the DPB, and/or a DPB index for the DPB parameter syntax structure of the target OLS. The DPB-related information may be syntax elements for the multi-layer index. For example, the DPB index may indicate a DPB parameter syntax structure of the target OLS. The syntax element for the width of the DPB is vps_ols_dpb_pic_width[MultiLayeredOlsIdx[TargetOlsIdx]], and the syntax element for the height of the DPB is vps_ols_dpb_pic_height [MultiLayeredOlsIdxmet[TargetOlsIdx] of the syntax element of the above-mentioned vps_ols_dpb_pic_height [MultiLayeredOlsIdxmet], the DPB) is the above-described vps_ols_dpb_chroma_format[MultiLayeredOlsIdx[TargetOlsIdx]], the syntax element for the bit depth of the DPB is the above-described vps_ols_dpb_bitdepth_minus8[MultiLayeredOlsIdx[TargetOls_Lams_idx]], the number of syntax elements of the above-mentioned vps_ols_Lams_idx .

For example, the encoding apparatus may derive the DPB parameter of the target OLS and may generate the DBP related information for the DPB parameter.

Meanwhile, for example, the encoding apparatus may perform a DPB management process based on the HRD parameter and/or the DPB parameter. For example, the encoding apparatus may perform a picture management process for the decoded picture of the DPB based on the HRD parameter and/or the DPB parameter. For example, the encoding apparatus may add a decoded picture to the DPB, or may remove a decoded picture in the DPB. For example, the decoded picture in the DPB may be used as a reference picture of inter prediction for the picture in the target OLS, or the decoded picture in the DPB may be used as an output picture. The decoded picture may mean a picture decoded before the current picture in decoding order in the target OLS.

The encoding apparatus encodes image information including the HRD-related information and the DPB-related information (S420). The encoding device may encode the HRD-related information and/or the DPB-related information. The image information may include the HRD-related information and/or the DPB-related information.

Meanwhile, the encoding apparatus may decode the picture of the target OLS. Also, for example, the encoding device may update the DPB based on the HRD-related information and/or the DPB-related information for the target OLS. For example, the encoding apparatus may perform a DPB management process for a decoded picture of a DPB based on the HRD-related information and/or the DPB-related information. For example, the encoding apparatus may add a decoded picture to the DPB, or may remove a decoded picture in the DPB. For example, the decoded picture in the DPB may be used as a reference picture of inter prediction for the picture in the target OLS, or the decoded picture in the DPB may be used as an output picture. The decoded picture may mean a picture decoded before the current picture in decoding order in the target OLS.

Also, for example, the encoding apparatus may decode the picture of the target OLS based on the DPB. For example, the encoding apparatus may derive a prediction sample by performing inter prediction on a block within the picture based on the reference picture of the DPB, and a reconstructed sample and/or reconstructed for the picture based on the prediction sample You can create a picture. Meanwhile, for example, the encoding apparatus may derive a residual sample from a block within the picture, and may generate a reconstructed sample and/or a reconstructed picture through addition of the prediction sample and the residual sample.

Meanwhile, for example, the encoding apparatus may generate and encode prediction information for a block of a picture of the target OLS. In this case, various prediction methods disclosed in this document, such as inter prediction or intra prediction, may be applied. For example, the encoding apparatus may determine whether to perform inter prediction or intra prediction on the block, and may determine a specific inter prediction mode or a specific intra prediction mode based on the RD cost. According to the determined mode, the encoding apparatus may derive a prediction sample for the block. The prediction information may include prediction mode information for the block. The image information may include the prediction information.

Also, for example, the encoding apparatus may encode residual information for a block of the picture.

For example, the encoding apparatus may derive the residual sample by subtracting the original sample and the predicted sample for the block.

Then, for example, the encoding apparatus may quantize the residual sample to derive a quantized residual sample, and may derive a transform coefficient based on the quantized residual sample, and based on the transform coefficient The residual information may be generated and encoded. Alternatively, for example, the encoding apparatus may quantize the residual sample to derive a quantized residual sample, transform the quantized residual sample to derive a transform coefficient, and based on the transform coefficient The residual information may be generated and encoded. The image information may include the residual information. Also, for example, the encoding apparatus may encode image information and output it in the form of a bitstream.

The encoding apparatus may generate reconstructed samples and/or a reconstructed picture through addition of the prediction samples and the residual samples. Thereafter, as described above, in-loop filtering procedures such as deblocking filtering, SAO and/or ALF procedures may be applied to the reconstructed samples in order to improve subjective/objective picture quality if necessary.

Meanwhile, the bitstream including the image information may be transmitted to the decoding device through a network or a (digital) storage medium. Here, the network may include a broadcasting network and/or a communication network, and the digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, and SSD.

5 schematically shows an encoding apparatus for performing an image encoding method according to this document. The method disclosed in FIG. 4 may be performed by the encoding apparatus disclosed in FIG. 5 . Specifically, for example, the entropy encoding unit of the encoding apparatus of FIG. 5 may perform S400 to S420. Also, although not shown, the process of performing the DPB management process may be performed by the DPB of the encoding apparatus, and the process of decoding the current picture may be performed by the prediction unit and the residual processing unit of the encoding apparatus. .

6 schematically shows an image decoding method by a decoding apparatus according to the present document. The method disclosed in FIG. 6 may be performed by the decoding apparatus illustrated in FIG. 3 . Specifically, for example, S600 to S610 of FIG. 6 may be performed by an entropy decoding unit of the decoding apparatus, and S620 of FIG. 6 may be performed by a DPB, a prediction unit, and a residual processing unit of the decoding apparatus. .

The decoding apparatus derives the multilayer OLS index of the target output layer set (OLS) in the list of multilayer output layer sets (OLS) (S600). The decoding apparatus may derive the multilayer OLS index of the target OLS in the list of multilayer OLSs. Here, for example, the multi-layer OLSs may be OLSs including a plurality of layers. Also, for example, the target OLS may be one of the multi-layer OLSs.

For example, the decoding apparatus may derive the multi-layer OLS index as shown in Table 4 above. For example, when the target OLS is the nth OLS among multilayer OLSs, the multilayer OLS index of the target OLS may be derived as n-1. For example, when the target OLS, which is the i-th OLS among all OLSs, is the n-th OLS among the multi-layer OLSs, the multilayer OLS index (MultiLayeredOlsIdx[i]) of the target OLS can be derived as n-1. have.

The decoding apparatus obtains Hypothetical Reference Decoder (HRD) related information and Decoded Picture Buffer (DPB) related information for the target OLS based on the multilayer OLS index (S610). The decoding apparatus may acquire Hypothetical Reference Decoder (HRD) related information and Decoded Picture Buffer (DPB) related information for the target OLS based on the multilayer OLS index.

For example, the decoding apparatus may acquire HRD-related information and/or DPB-related information for the multi-layer index. For example, HRD-related information and / or the DPB related information vps_ols_dpb_pic_width [MultiLayeredOlsIdx [TargetOlsIdx]], vps_ols_dpb_pic_height [MultiLayeredOlsIdx [TargetOlsIdx]], vps_ols_dpb_chroma_format [MultiLayeredOlsIdx [TargetOlsIdx]], vps_ols_dpb_bitdepth_minus8 [MultiLayeredOlsIdx [TargetOlsIdx]], vps_ols_dpb_params_idx [MultiLayeredOlsIdx [ TargetOlsIdx]] and/or vps_ols_hrd_idx[MultiLayeredOlsIdx[TargetOlsIdx]].

For example, the HRD-related information may include an HRD index for an HRD parameter syntax structure of the target OLS. The HRD index may be an HRD index for the multi-layer index. For example, the HRD index may indicate an HRD parameter syntax structure of the target OLS. The syntax element of the HRD index may be the aforementioned vps_ols_hrd_idx[MultiLayeredOlsIdx[TargetOlsIdx]].

Also, for example, the DPB-related information includes a syntax element for the width of a decoded picture buffer (DPB) for the target OLS, a syntax element for the height of the DPB, and a chroma format of the DPB. It may include a syntax element for the DPB, a syntax element for the bit depth of the DPB, and/or a DPB index for the DPB parameter syntax structure of the target OLS. The DPB-related information may be syntax elements for the multi-layer index. For example, the DPB index may indicate a DPB parameter syntax structure of the target OLS. The syntax element for the width of the DPB is vps_ols_dpb_pic_width[MultiLayeredOlsIdx[TargetOlsIdx]], and the syntax element for the height of the DPB is vps_ols_dpb_pic_height [MultiLayeredOlsIdxmet[TargetOlsIdx] of the syntax element of the above-mentioned vps_ols_dpb_pic_height [MultiLayeredOlsIdxmet], the DPB) is the above-described vps_ols_dpb_chroma_format[MultiLayeredOlsIdx[TargetOlsIdx]], the syntax element for the bit depth of the DPB is the above-described vps_ols_dpb_bitdepth_minus8[MultiLayeredOlsIdx[TargetOls_Lams_idx]], the number of syntax elements of the above-mentioned vps_ols_Lams_idx .

The decoding apparatus decodes the picture in the target OLS based on the HRD-related information and the DPB-related information (S620).

For example, the decoding apparatus may derive an HRD parameter for the target OLS based on the HRD-related information. For example, the decoding apparatus may derive the HRD parameter of the target OLS based on the HRD parameter syntax structure of the target OLS derived based on the HRD index. Also, for example, the decoding apparatus may derive a DPB parameter for the target OLS based on the DPB-related information.

For example, the decoding apparatus may perform a DPB management process for a decoded picture buffer (DPB) based on the HRD parameter and/or the DPB parameter for the target OLS. For example, the decoding apparatus may perform a picture management process for the decoded picture of the DPB based on the HRD parameter and/or the DPB parameter. For example, the decoding apparatus may add a decoded picture to the DPB, or may remove a decoded picture in the DPB. For example, the decoded picture in the DPB may be used as a reference picture of inter prediction for the picture in the target OLS, or the decoded picture in the DPB may be used as an output picture. The decoded picture may mean a picture decoded before the current picture in decoding order in the target OLS.

For example, the decoding apparatus may decode the picture in the target OLS based on the DPB on which the DPB management process is performed. For example, the decoding apparatus may derive a prediction sample by performing inter prediction on a block within the picture based on the reference picture of the DPB, and a reconstructed sample and/or reconstructed for the picture based on the prediction sample You can create a picture. On the other hand, for example, the decoding apparatus may derive a residual sample in the block in the picture based on the residual information received through the bitstream, and through the addition of the prediction sample and the residual sample, a reconstructed sample and / or a restored picture may be generated.

Thereafter, as described above, in-loop filtering procedures such as deblocking filtering, SAO and/or ALF procedures may be applied to the reconstructed samples in order to improve subjective/objective picture quality if necessary.

7 schematically shows a decoding apparatus for performing an image decoding method according to this document. The method disclosed in FIG. 6 may be performed by the decoding apparatus illustrated in FIG. 7 . Specifically, for example, the entropy decoding unit of the decoding apparatus of FIG. 7 may perform S600 to S610 of FIG. 6 , and the DPB, prediction unit, and residual processing unit of the decoding apparatus of FIG. 7 perform S620 of FIG. 6 . can do.

According to this document described above, it is possible to efficiently perform signaling of HRD-related information and DPB-related information by deriving an index of a list for multi-layer OLS among all OLSs, thereby improving overall coding efficiency.

In addition, according to this document, it is possible to prevent HRD-related information and DPB-related information signaled only for multi-layer OLS from being mapped to wrong OLS by deriving an index of a list for multi-layer OLS among all OLSs. Coding efficiency can be improved.

In the above embodiment, the methods are described on the basis of a flowchart as a series of steps or blocks, but this document is not limited to the order of the steps, and some steps may occur in a different order or concurrently with other steps as described above. have. In addition, those skilled in the art will understand that the steps shown in the flowchart are not exhaustive and that other steps may be included or that one or more steps of the flowchart may be deleted without affecting the scope of this document.

Embodiments described in this document may be implemented and performed on a processor, microprocessor, controller, or chip. For example, the functional units shown in each figure may be implemented and performed on a computer, a processor, a microprocessor, a controller, or a chip. In this case, information for implementation (ex. information on instructions) or an algorithm may be stored in a digital storage medium.

In addition, the decoding device and the encoding device to which the embodiments of this document are applied are a multimedia broadcasting transceiver, a mobile communication terminal, a home cinema video device, a digital cinema video device, a surveillance camera, a video conversation device, and a real-time communication device such as a video communication device. , mobile streaming device, storage medium, camcorder, video on demand (VoD) service providing device, OTT video (Over the top video) device, internet streaming service providing device, three-dimensional (3D) video device, video telephony video device, means of transport It may be included in a terminal (eg, a vehicle terminal, an airplane terminal, a ship terminal, etc.) and a medical video device, and may be used to process a video signal or a data signal. For example, the OTT video (Over the top video) device may include a game console, a Blu-ray player, an Internet-connected TV, a home theater system, a smart phone, a tablet PC, a digital video recorder (DVR), and the like.

In addition, the processing method to which the embodiments of this document are applied may be produced in the form of a program executed by a computer, and may be stored in a computer-readable recording medium. Multimedia data having a data structure according to this document may also be stored in a computer-readable recording medium. The computer-readable recording medium includes all types of storage devices and distributed storage devices in which computer-readable data is stored. The computer-readable recording medium includes, for example, Blu-ray Disc (BD), Universal Serial Bus (USB), ROM, PROM, EPROM, EEPROM, RAM, CD-ROM, magnetic tape, floppy disk and optical It may include a data storage device. In addition, the computer-readable recording medium includes a medium implemented in the form of a carrier wave (eg, transmission through the Internet). In addition, the bitstream generated by the encoding method may be stored in a computer-readable recording medium or transmitted through a wired/wireless communication network.

In addition, the embodiments of this document may be implemented as a computer program product using program codes, and the program codes may be executed in a computer according to the embodiments of this document. The program code may be stored on a carrier readable by a computer.

8 is an exemplary view of a content streaming system structure to which embodiments of this document are applied.

A content streaming system to which embodiments of this document are applied may largely include an encoding server, a streaming server, a web server, a media storage, a user device, and a multimedia input device.

The encoding server generates a bitstream by compressing content input from multimedia input devices such as a smart phone, a camera, a camcorder, etc. into digital data and transmits it to the streaming server. As another example, when multimedia input devices such as a smartphone, a camera, a camcorder, etc. directly generate a bitstream, the encoding server may be omitted.

The bitstream may be generated by an encoding method or a bitstream generating method to which embodiments of this document are applied, and the streaming server may temporarily store the bitstream in the process of transmitting or receiving the bitstream.

The streaming server transmits multimedia data to the user device based on a user's request through the web server, and the web server serves as a mediator informing the user of a service. When a user requests a desired service from the web server, the web server transmits it to a streaming server, and the streaming server transmits multimedia data to the user. In this case, the content streaming system may include a separate control server. In this case, the control server serves to control commands/responses between devices in the content streaming system.

The streaming server may receive content from a media repository and/or an encoding server. For example, when content is received from the encoding server, the content may be received in real time. In this case, in order to provide a smooth streaming service, the streaming server may store the bitstream for a predetermined time.

Examples of the user device include a mobile phone, a smart phone, a laptop computer, a digital broadcasting terminal, a personal digital assistant (PDA), a portable multimedia player (PMP), a navigation system, a slate PC, Tablet PC (tablet PC), ultrabook (ultrabook), wearable device (e.g., watch-type terminal (smartwatch), glass-type terminal (smart glass), HMD (head mounted display)), digital TV, desktop There may be a computer, digital signage, and the like. Each server in the content streaming system may be operated as a distributed server, and in this case, data received from each server may be distributed and processed.

The claims described herein may be combined in various ways. For example, the technical features of the method claims of the present specification may be combined and implemented as an apparatus, and the technical features of the apparatus claims of the present specification may be combined and implemented as a method. In addition, the technical features of the method claim of the present specification and the technical features of the apparatus claim may be combined to be implemented as an apparatus, and the technical features of the method claim of the present specification and the technical features of the apparatus claim may be combined and implemented as a method.

Claims (15)

In the image decoding method performed by the decoding device, deriving a multi-layer OLS index of a target OLS in a list of multi-layer output layer sets (OLS); obtaining Hypothetical Reference Decoder (HRD) related information and Decoded Picture Buffer (DPB) related information for the target OLS based on the multi-layer OLS index; and Decoding the picture in the target OLS based on the HRD-related information and the DPB-related information, The multi-layer OLSs are OLSs including a plurality of layers, The target OLS is one of the multi-layer OLS. According to claim 1, The HRD-related information comprises an HRD index for an HRD parameter syntax structure of the target OLS. 3. The method of claim 2, The decoding of the picture in the target OLS based on the HRD-related information and the DPB-related information includes: and deriving an HRD parameter of the target OLS based on the HRD parameter syntax structure of the target OLS derived based on the HRD index. According to claim 1, The DPB-related information includes a syntax element for the width of a decoded picture buffer (DPB) for the target OLS, a syntax element for the height of the DPB, a syntax element for the chroma format of the DPB, and the DPB A method for decoding an image, comprising: a syntax element for a bit depth of , and a DPB index for a DPB parameter syntax structure of the target OLS. 5. The method of claim 4, The decoding of the picture in the target OLS based on the HRD-related information and the DPB-related information includes: and deriving the DBP parameter of the target OLS based on the DPB-related information. In the video encoding method performed by the encoding device, deriving a multi-layer OLS index of a target OLS in a list of multi-layer output layer sets (OLS); generating Hypothetical Reference Decoder (HRD) related information and Decoded Picture Buffer (DPB) related information for the target OLS based on the multilayer OLS index; and encoding image information including the HRD-related information and the DPB-related information; The multi-layer OLSs are OLSs including a plurality of layers, The video encoding method according to claim 1, wherein the target OLS is one of the multi-layer OLSs. 7. The method of claim 6, The HRD-related information comprises an HRD index for an HRD parameter syntax structure of the target OLS. 8. The method of claim 7, The generating of the HRD-related information and the DPB-related information for the target OLS based on the multi-layer OLS index includes: generating the HRD parameter syntax structure of the target OLS; and and generating the HRD index indicating the HRD parameter syntax structure of the target OLS. 7. The method of claim 6, The DPB-related information includes a syntax element for the width of the DPB for the target OLS, a syntax element for the height of the DPB, a syntax element for the chroma format of the DPB, and a bit depth of the DPB. An image encoding method comprising a syntax element and a DPB index for the DPB parameter syntax structure of the target OLS. 10. The method of claim 9, The generating of the HRD-related information and the DPB-related information for the target OLS based on the multi-layer OLS index includes: deriving a DPB parameter of the target OLS; and and generating the DBP related information for the DPB parameter. A computer readable digital storage medium storing a bitstream including image information causing a decoding apparatus to perform an image decoding method, the image decoding method comprising: deriving a multi-layer OLS index of a target OLS in a list of multi-layer output layer sets (OLS); obtaining Hypothetical Reference Decoder (HRD) related information and Decoded Picture Buffer (DPB) related information for the target OLS based on the multi-layer OLS index; and Decoding the picture in the target OLS based on the HRD-related information and the DPB-related information, The multi-layer OLSs are OLSs including a plurality of layers, and the target OLS is one of the multilayer OLSs. 12. The method of claim 11, The HRD-related information includes an HRD index for an HRD parameter syntax structure of the target OLS. 13. The method of claim 12, The decoding of the picture in the target OLS based on the HRD-related information and the DPB-related information includes: and deriving an HRD parameter of the target OLS based on the HRD parameter syntax structure of the target OLS derived based on the HRD index. 12. The method of claim 11, The DPB-related information includes a syntax element for the width of a decoded picture buffer (DPB) for the target OLS, a syntax element for the height of the DPB, a syntax element for the chroma format of the DPB, and the DPB A computer-readable digital storage medium comprising a syntax element for a bit depth of , and a DPB index for a DPB parameter syntax structure of the target OLS. 15. The method of claim 14, The decoding of the picture in the target OLS based on the HRD-related information and the DPB-related information includes: and deriving a DBP parameter of the target OLS based on the DPB-related information.

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